Keratoconus

This is an uncommon, degenerative disease inherited as an autosomal recessive or autosomal dominant trait. It affects all races and often presents in the second decade of life. It may be associated with a number of characteristic syndromes.

• Keratoconus is a progressive disease in which the normal cornea becomes more irregular in shape over time resulting in astigmatism, and can progress to a stage where the cornea becomes thinner and begins to bulge into a cone-like shape
  • in severe disease the cornea is cone shaped and the lower lid is indented by the cornea when the patient gazes downwards (Munson's sign)
  • corneal distortion prevents clear visualisation of the fundus
• characteristically, there is blurred vision, most commonly bilateral
• in mild to moderate keratoconus, spectacles or a range of contact lenses may help as well as treatment with riboflavin eye drops. In more severe disease, penetrating or deep lamellar keratoplasty corneal grafting (transplantation) to restore the normal corneal shape may be required
  • corneal implants are flexible, crescent-shaped rings of polymethyl methacrylate that are placed in the periphery of the cornea
    • affect refraction in the eye by physically changing the shape of the cornea, flattening the front of the eye, and so correcting the irregular corneal shape
    • procedure is undertaken under local or general anaesthesia
• the condition is slowly progressive between the ages of 20 and 60 years. Prognosis may be excellent if a corneal transplant is performed before extreme corneal thinning occurs